Its been in my tank for 16 months now and it honestly looks the same and feels the same as the day i got it. It doesnt seem to break down into mush, if thats what you were afraid of. Although i've only had it for a year and a half, it seems that it could last much longer.
As for DE, i havent tried to keep any shrimp so I cant tell you much. I do have snails that do very well.
The downside is that I want a different color substrate ... the upside is that i'm only out 12 bucks if i get something new because the litter is so cheap